Interface phenomena at semiconductor heterojunctions: Local-density valence-band offset in GaAs/AlAs

The valence-band offset Δ$E_v$ at the lattice-matched GaAs/AlAs(001) interface is derived from highly precise self-consistent all-electron local-density band-structure calculations of the (GaAs${)}_n$(AlAs${)}_n$(001) superlattices (with n≤3). We calculate Δ$E_v$ by using the core levels—available uniquely from an all-electron approach—as reference energies. Since these are experimentally accessible quantities, a direct comparison with experiment is, in principle, possible. We find that Δ$E_v$=0.5±0.05 eV, in very good agreement with recent experimental results (Δ$E_v$=0.45–0.55 eV). Calculated core-level shifts are also compared with experiment. These results, which are closely related to changes in the charge-density distribution at the interface, contribute to understanding the underlying mechanism of the band discontinuity.